He has found more than 500 references, from Homer onwards, to a ‘first sleep’ that lasted until maybe midnight, and was followed by ‘second sleep’.

In between the two, people routinely got up, peed, smoked, read, chatted, had friends round, or simply reflected on the events of the previous day – and on their dreams. (Plenty also had sex, by all accounts far more satisfactorily than at the end of a hard day’s labouring. Couples who copulated ‘after the first sleep, wrote a 16th-century French doctor, ‘have more enjoyment, and do it better’.)

Experiments by Dr Thomas Wehr at America’s National Institute of Mental Health appear to bear out the theory that this two-part slumber is man’s natural sleeping pattern: a group of young male volunteers deprived of light at night for weeks at a time rapidly fell into the segmented sleep routine described in so many of Ekirch’s documentary sources. It could even be, Wehr has theorised, that many of today’s common sleeping disorders are essentially the result of our older, primal habits “breaking through into today’s artificial world.’”– Jon Henley, “The Dark Ages,” The Guardian (London), October 24, 2009